import Dep from "./Dep.js";

export default class Watcher {
  constructor(vm, el, vmKey) {
    // 做一些信息的初始化
    this.vm = vm;
    this.el = el;
    this.vmKey = vmKey;
    Dep.target = this;
    this.update();
    Dep.target = null;
  }
  update() {
    if (this.el.nodeType === Node.TEXT_NODE) {
      this.el.nodeValue = this.vm[this.vmKey];
    } else if (this.el.nodeType === Node.ELEMENT_NODE) {
      this.el.innerHTML = this.vm[this.vmKey];
    }
  }
}
